Electrical switch



Nov. 1l, 1941. H, J, CRABBS ELEGTRICAL SWITCH Filed April 20, 1939' 2Sheets-Sheet l rm l 7 v I f7 f y d J/ if w /22 ...MW w M m f2 3 J Y o lI j. 2 2

INVENToR /@fefZJCfabs J W ATToR EY Nov. 1l, 1941. H. J. CRABBS2,262,168" I ELECTRICAL SWITCH Filed April 20, 1939 2 She'ets--Sheeii 2ff y (7J Huf/ ff BY 5f 25j! WM Patented Nov. 11, 1941 2,262,168ELECTRICAL SWITCH Herbert J. Crabbs, Wilkinsburg, Pa., assignor toWestinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., acorporation of Pennsylvania Application April 20, 1939, Serial No.268,906

(Cl. 20D-162) 23 Claims.

The invention relates to electrical switches in general, and moreparticularly to switches designed for high current carrying capacity andemployed in moderate and high-voltage electrical transmission ordistribution systems and to methods of forming the Contact elements.

In switches of the above-mentioned type, it has been found desirable toprovide the blades with raised contact portions to restrict the Contactarea at both ends of the switch. This construction, together with theusual spring cup washers, provides a relatively high contact pressureper unit of contact area, making an efcient electrical joint.

In this type of construction, as well as in other types even whererestricted contact area is not provided. considerable difficulty hasbeen experienced in making the blade contact portions contact properlywith the tongues. It is apparent that to prevent any-1ocalized points ofcontact and to show uniform abrasion or marking on the tongues, theblades and tongues must be perfectly true and perfectly lined up witheach other. This is entirely impractical from a manufacturingstandpoint, as no matter how carefully machined, the edges of the4tongues seem to be higher than the central surface. 'This may be onlyon the order of a fraction of a thousandth of an inch, yet it is enoughto produce localized points of contact and a poorly marked contact.

Some trouble has also been experienced with galling of the contactportions, particularly at the hinge .end of the switch. This resultsfrom the entry of abrasive dirt or material between the contactingportions.

An object of the present invention is the provision of anl improvedelectrical switch which provides proper and uniform Contact between theblades and tongues and uniform marking of the contacts, even though theparts are not specially trued and perfectly aligned.

Another object of the invention is the provision of an electrical switchof improved construction which provides uniform restricted area contactand uniform contact marking.

Another object of the invention is the provision of an electrical switchhaving an improved construction which provides uniform limited areacontacts and uniform contact marking without requiring any specialmachining, truing and aligning of the parts.

Another object of the invention is the provision of an electrical switchhaving an improved contact construction which prevents galling of thecontacts.

Another object of the invention is the provision of an electrical switchhaving an improved construction which provides uniform restricted areacontact at'the hinge end, and which seals out the dirt to preventgalling of the contact, and which also seals in the lubricant so as tokeep the hinge contact permanently lubricated.

Another object of the invention is the provision of methods for formingContact elements having the characteristics noted above.

Another object of the invention is the provision of an improvedelectrical switch, as described in the preceding paragraphs, which issimple, reliable in operation, and inexpensive to manufacture andassemble.

In carrying out the invention, the break end of each switch blade isembossed to provide a raised contact portion having a serrated orknurled contact surface, thus providing a multiplicity of lines, ridgesor points on the contact surface. The copper switch blades with orwithout an overlaid silver surface have bodies that can be deformed withrelative ease. With this construction, even' though the blades are notaccurately aligned with the tongues and both are not perfectly flat andtrue, a uniform and proper contact over the entire contact length anduniform tongue marking is obtained. This is accomplishedby reason of thefact that any of the lines, ridges or points which touch the tongue rstdue to the parts not being true and perfectly aligned, will wear down orcut into the tongue after a few successive opening and closingoperations of the switch until all of the ridges, lines, or

" points finally Contact with the, tongue.

The hinge ends of the switch blades are also embossed to provide araised Contact portion having concentric circular serrations or ridges.The ridges wear in as the switch operates until all of the ridgescontact with the tongue. As soon as the outer ridges contact with thetongue, they forma seal against external dirt or foreign matter gettinginto the Contact, and also act to seal in whatever lubricant is used,thus keeping the contact permanently lubricated.

The novel features that are considered characteristic of the inventionare set forth in particular in the appended claims. The inventionitself, however, both as to construction and operation, together withadditional objects and advantages thereof, will best be understood fromthe following detailed description of several embodiments thereof whenread in conjunction with the accompanying drawings, in which:

Figure 1 is a plan view of an electrical switch constructed inaccordance with the invention;

Fig. 2 is a side elevational view of the switch shown in Fig. 1;

Fig. 3 is an enlarged side elevational view of one of the switch bladesshowing the inner side of the blade;

Fig. 4 is an enlarged plan view of the switch blade;

Fig. 5 is an enlarged fragmentary cross-sectional view of the raisedcontact portion at the break end of the switch blade;

Fig. 6 is an enlarged fragmentary side elevational view of a switchblade having a slightly modied raised contact portion;

Fig. '1 is a fragmentary enlarged cross--sectional view of the raisedContact construction shown in Fig. 6;

Fig. 8 is an enlarged fragmentary side elevational view of a switchblade having a further modified raised contact portion;

Fig. 9 is a fragmentary plan view of `the switch blade shown in Fig. 8;and

Fig. 10 is an enlarged sectional view through the hinge end of theswitch.

Referring to the drawings, and particularly to Figsyl and 2 thereof, thereference numeral II designates a rigid supporting base upon which ismounted a pair of spaced insulating columns I3 for supporting theswitch. The insulating columns I3 are preferably formed of vitreousmaterial, such as porcelain or the like, and are secured to the base IIby means of a plurality of bolts I5.

A pair of switch terminals I1 and I9 are rigidly secured, as by bolts2I, to the metal caps 23 of the insulating columns I3. The terminals I1and I9 are of conducting material, preferably copper, or a suitablealloy of copper, and are provided with generally rectangular, flatcontact tongues and 21, respectively, which project outwardly from theflat bases of the terminals. The contact tongues 25 and 21 may be formedintegral with the terminals or may constitute separate elements whichare secured to the terminals in any suitable manner, as, for example, bywelding. Each of the terminals is also provided with an integralterminal connecting portion 29, which projects beyond the end of theswitch and serves for connecting electrical conductors to the switchterminal.

One of the terminals I1 serves as a hinge terminal, and a pair ofmechanically connected switch blades 3I are pivoted at one end by meansof a through bolt 33 to the contact tongue 25 of this hinge terminal I1.The blades are: thus mounted for swinging movement into and out ofengagement with the break contact tongue 21 of the break terminal I9.

The switch blades 3I are composed of flat metal bars, preferably ofcopper, and are mounted to engage the opposite sides of the contacttongues 25 and 21. The two blades are mechanically connected togetheradjacent their free ends by means of a through bolt 35%, and the bladesare biased towards each other to engage the contact tongues with apredetermined pressure by means of the spring cup washers 31. The cupwashers 31 are mounted on the through bolts 33 and 35 at the hinge andbreak ends of the switch, and are held in tension against the outersides of the two blades by means of the heads of the through bolts andby the nuts 39 threaded on the ends of the through bolts. v

. The break contact tongue 21 is provided with a recess adjacent itsouter end for accommodating the through bolt when the switch is closed,and the outer edges of this break contact tongue 21 are beveled, asindicated in Fig. 1, to facilitate closing of the switch. The bevelededges serve to guide the free ends of the switch blades 3l onto thebreak tongue 21 and also act as wedges to spread the free ends of theblade during closing of the switch.

A latch device is provided for releasably latching the switch blades 3|in closed position. This latch device comprises a latch 4I which ispivotally mounted at 43 on the break terminal I9 beyond the contacttongue 21, and a latch pin 45 carried by the free ends of the blades andextending transversely therebetween. The pivoted latch 4I is biased tolatching position by a spring 41, and the nose 49 of the pivoted latchis adapted to extend in the space between the free ends of the blades 3Iand to engage the latch pin 45 when the blades are in closed position toreleasably lock the blades in this position.

An operating eye 5I is pivotally mounted between the free ends of theblades 3I by means of a through bolt 53, and this operating eye has aprojecting arm formed integral therewith which is adapted to engage theinclined edge of the nose 49 of the latch 4I when the switch is closed.The operating eye 5I serves as a means for releasing the latch, and foroperating the switch blades 3I to open and closed circuit position.

When the operating eye 5I is pulled to open n the switch, it firstoperates to force back and release the latch 4I to free the switchbladesfor opening movement. Further pull on theoperating eye pries theblades out of their high pressure engagement with the break tongue 21,and thereafter moves the blades 3| about their pivot axis 33 to openposition. A stop pin 51, extending transversely between the blades, isadapted to engage the projecting arm 55 of the operating eye 5I to limitclockwise rotation of the operating eye on its pivot bolt 53, thuspermitting the eye to be pushed to effect closing of the switch. Thelatch pin 45 also serves as a stop to limit counter-clockwise rotationof the operating eye 5I about its pivot axis 53 during open- Y ing ofthe switch.

The operating eye and the latch device are preferably of the samegeneral type and construction as fully described and claimed in mycopending application for Electrical switches, Serial No. 180,394, filedDecember 17, 1937, and assigned to the assignee of the presentinvention.

It has been found desirable to restrict the contact area at both thehinge and break ends of the switch to an order substantially that ofline or point contacts, or at least to an order considerably less thanthat of the transversely aligned surfaces. This provides a high contactpressure per unit of contact area, resulting in a very good and eicientelectrical joint. This restricted contact area is obtained in one way byproviding the switch blade or blades with elongated raised contactportions at the break end and with annular raised contact portions atthe hinge end concentric with the pivot axis. The raised contactportions engage the flat surfaces of the contact tongues and thusrestrict the contact area.

As has previously been pointed out, onevery important difficulty thathas been experienced with this general type of switch, as well as withother types, has been in making the contact portions of the bladescontact uniformly with the contact tongue. This is necessary to preventlocalized points of contact and to obtain uniform abrasion or marking ofthe contact tongue. It is apparent that to obtain uniform contact and toshow uniform abrasion or marking of the contact tongue, the blades andtongues must be perfectly true and perfectly lined up with each other.This is impractical from a manufacturing standpoint. No matter howcarefully machined, the edges of the tongues seem to be higher than thecentral surface thereof. This may be only on the order of a fraction ofa thousandth of an inch, but it is enough to produce a localized pointof contact and poorly marked contact tongue. This is also true of theends of the raised portions on the switch blades.

The present invention provides a switch having restricted area contactswhich provide uniform contact and uniform markings on the contacttongues, and these results are obtained in a simple and economicalmanner without requiring any special truing, aligning and machiningoperations. In accordance with the present invention, the switch bladesare provided with raised Contact portions ofy restricted area having aknurled or serrated contact surface forming a multiplicity of ridges,lines or points for engaging the contact tongue. The copper bladecontact member, with or without an overlaid silver surface, has a bodythat can be deformed with relative ease. The size of the ridges, linesor points is such that any of the ridges, lines or points which contactthe contact tongue first, due to the contact members not being perfectly.true or perfectly lined up with each other, will wear in or iron downafter` a few operations of the switch until finally all of the raisedridges, lines or points Contact with the tongue. This gives uniform andproper contact over the entire contact length and also provides uniformmarking of the contact tongue, even though the tongues and blades arenot perfectly true and are not perfectly lined up with each other.

Referring to Fig. 3, each of the switch blades 3l is provided adjacentits free end with an elongated raised contact portion 59 having aknurled contact surface 6| of cross-hatch or waffle-iron design forminga multiplicity of relatively sharp projecting points. 63 (see Fig. 5).

The raised contact portion 59 and its knurled contact surface 6| isembossed on the blade by pressing the material out of the principalplane of the blade in an embossing die of the desired conguration.

The elongated raised contact portion may be provided with a knurledcontact surface consisting of a multiplicity of parallel relativelysharp-edged ridges, as shown in Figs. 6 and 7, instead of thecross-hatch or waffle-iron design shown in Fig. 3. In the modificationof the invention shown in Figs. G and 7, the switch blades 3l areprovided with elongated raised contact portions 65 having a knurledsurface 61 forming a multiplicity of parallel relatively sharp-edgedridges G9 for engaging the contact tongue of the switch. The raisedcontact portion 65 and its knurled surface 61 are embossed on the switchblade by a pressing operation in a suitable embossing die of the desiredconfiguration the same as in the embodiment of the invention shown inFig. 3. The embossing die in this modification has a surfaceconfiguration to provide the elongated raised contact portion 65 and themultiplicity of parallel sharp-edged ridges thereon as shown in Figs. 6and '7.

A further modification of `the invention is shown in Fig. 8. In thismodification, the switch blades 3l are provided with two raised contactportions 1I of relatively short length having knurled contact surfaces'I3 forming a plurality of relatively sharp-edged ridges similar to theknurled surface shown in Fig. 6. In this modification, the length of theraised contact portions 1l is shorter than the width between theadjacent edges of the contact tongue, the outline of the contact tonguebeing shown by the dotted lines 15 in Fig. 8. The raised contactportions 'll and their knurled surfaces are embossed on the switchblades 3l in the same manner as previously described in connection withthe other embodiments of the invention. The relatively short length ofthe raised contact portions 1l and Vtheir arrangement permit them toengage the more perfectly flat portions of the contact tongue, avoidingthe tongue edges.

The relatively sharp edged parallel ridges on the contact portions ofthe blades are preferably disposed parallel to the direction of motionof the contact portion of the blade as shown in Figs. 6 and 8, so thatthe ridges run onto and off of the stationary vcontact tongue in themanner of sled runners, each ridge making its own track on the surfaceof the contact tongue and always moving over the same track. With thisarrangement the ridges will wear down or cut their own grooves or tracksinto the contact tongue so as to uniformly engage the tongue throughouttheir entire length.

In all of the embodiments thus far described, the relatively sharp-edgedraised ridges 69, 1I or the relatively sharp contact points 63 of theraised contact portions of the blades are made of such size that any ofthe ridges or points which engage the contact tongue first to theexclusion of the others, due to the blades and Contact tongues not beingperfectly true or perfectly aligned, will wear down or cut into thesurface of the contact tongue after a relatively few opening and closingoperations of the switch until finally all of the ridges or pointscompletely engage the contact tongue. This provides a uniform contactthroughout the contact length and also provides uniform marking of thecontact members.

Referring to Figs. 3, 4 and l0, the hinge end of each of the switchblades 3| is provided with an annular contact portion 11 which is raisedabove the surface of the blade to restrict the contact area at the hingeend of the switch. The surface of the raised annular contact portion 11is knurled or serrated to provide a multiplicity of concentricallyarranged ridges 19 for engaging the hinge contact tongue 25. The raisedannular contact portions l1 and their concentric ridges 19 are embossedon the blades by pressing the same out of the material of the blade in asuitable embossing die in the same manner as the contact portions at thebreak end of the blades.

The concentrically arranged ridges 19 on the surface of the raisedcontact portions 1l have relatively sharp edges and are of a size suchthat any of these ridges which touch the hinge tongue first to theexclusion of others. due to the blades and tongue not being perfectlytrue or being perfectly aligned, will wear down in a few opening andclosing operations of ,the switch until finally all of the ridges 19completely engage the hinge tongue 25. The construction thus providesmultiple line restricted area contacts at the hinge end of the switchwith uniform contact over the entire .contact area and uniform markingof the hinge tongue.

As soon as the edges of the outer ridges 19 engage the surface of thehinge tongue 25, these ridges '19l where it will not cause galling ofthel contacts. The knurled surface of the raised contact portions at thebreak ends of the blades also serves to prevent galling of the contacts.

The outer ridgesfl when in engagement with' the surface of the hingetongue also act to seal in whatever lubricant is used for the hinge endof the switch, thus keeping the contact permanently lubricated.

If desired, the contact portions of the switch blades and the contactportions of the tongues may be provided with a silver surface to providesilver-to-silverv contact. be added to the contact portions of theswitch blades either before or after embossing the raisedcontactvportions on the blades. The copper switch blade, either with orwithout an overlaid silver surface, has a body which can be deformedwith relative ease so that the blades can be easily embossed to providethe raised Contact portions disclosed, and also so that the raisedridges or points which first touch the contact tongue will readilyweandown in a .few Operations of the -switch to an extent such thatnally all of the ridges or contact points will completely engage thecontact tongues.

While the raised contact portions with their knurled Contact faces havebeen disclosed as being formed on the switch blades, it is to beunderstood that these raised contact portions may Lbe provided on thestationary contact tongues instead of on the blades, if desired. Also,the contact portions have been disclosed as being formed on the Contactmembers by an embossing operation in a suitable embossing die. Whileythis is the preferred method of forming the contact portions, it is tobe understood that the raised contact portions and their knurled contactsurface may be provided on the contact members in Various other ways.For example, the sharp edged rid-ges or projections could be provided bymilling the same. The raised contact portions may be formed integralwith the blades or as separate elements to be secured to the blades.

The invention thus provides an improved construction havingmultiple lineor point restricted area contacts which provide uniform contact over theentire/restricted contact area, and which give uniform marking of thecontact tongues or members. The multiple line or point restricted areacontactsy are provided ina very simple and economical manner, and theuniform contact and' Contact vmarking are obtained by the constructionwithout requiring any special truing, aligning or machining operations.

While the invention has -been disclosed in accordance with the patentstatutes, it is to be understood that Various changes in the structural`details thereof may be made without The silver surface mayv departingfrom the spirit of the invention. It is desired, therefore, that thelanguage of the appended claims be given th'e broadest reasonableinterpretation permissible in the light of the prior art.`

I claim as my invention:

1,. In an electrical switch, a pair of relatively movable contactmembers having the form of flat metal bars, one of said members having araised contact portion of restricted area provided with a knurledcontact surface.

2. In an electrical switch, a pair of relatively 'movable contactmembers having the form of flat metal bars, one of said members having'a raised restricted area Contact portion provided with a knurled contactsurface forming a multiplicity of parallel relatively sharp edged ridgesfor engaging the other of said members.

3. In an electrical switch, a contact member, a switch blade movable,into and out of engagement with said contact member, said blade beingprovided with an embossed contact portion having a serrated contactsurface for engaging said contact member.

4, In an electrical switch, a pair of relatively movable contact membershaving the form of flat metal bars, one of said members being providedwith an embossed contact portion having a knurled contact surfaceforming a multiplicity of parallel relatively sharp edged .ridges forengaging the surface of the other member.

5. In an electrical switch, a pair of fiat contact members, meansmounting said members in substantially parallel planes for relativemovement into and out of engagement, one of said members having a raisedrestricted area contact portion pressed out of the principal plane ofthe member, said contact portion being provided with a. knurled contactsurface for engaging the surface of the other member when the switch isclosed.

6. In an electrical switch, a pair of spaced blade members, a hingecontact, a tongue contact, means pivotally mounting said blade memberson said hinge contact for swinging movement into and out of engagementwith said tongue Contact, spring means pressing said blades towards eachother, said blade members being provided with raised Contact portionshaving knurled contact surfaces forming a multiplicity of parallelrelatively sharp edged ridges for en-` gaging said contactsto restrictthe contact area.

7. A contact member for an electrical switch, said contact membercomprising a flat metal bar provided with a raised contact portionhaving a multiplicity of relatively sharp edged parallel ridges on itscontact face.

8. In an electrical switch, a. pair of fiat contact members, meansmounting said members in substantially parallel planes for relativemovement into mutual engagement, one of said contact members having araised restricted-arca contact portion provided with a knurled contactsurface of silver for engaging the contact sur-- face of the othermember which is also of silver.

9. In an electrical switch, va pair of flat contact members, meansmounting said members insubstantially parallel planes for relativemovement into mutual engagement, one of said members being provided witha raised contact portion having a knurled surface for engaging the sur--face of the other member, said raised contact portion being constitutedby die-.pressing the material out of the principal plane of the blademember.

10. In an electrical switch, a pair of'eilat contact members, meansmounting said members in substantially parallel planes for relativemovement into mutual engagement, one of said members being provided witha raised restricted area contact portion having a multiplicity ofclosely spaced relatively sharp projections for engaging the surface ofthe other member, the size of said projections being such that any whichcontact the other contact member rst will wear down in a few operationsof said switch until nally all of said projections contact with saidother contact member.

11. A switch comprising a hinge contact member, a blade member pivotedthereon, one of said members being provided with an annular raisedcontact portion concentric with the pivot axis, and having a pluralityof concentric relatively sharp-edged ridges thereon for engaging theother of said members.

l2. A switch comprising a hinge contact member, a blade member pivotedthereon, one of said members being provided with a contact portionhaving a plurality of sharp-edged circular ridges concentric with thepivot axis for engaging the surface of the other member, said ridgesbeing of a size such that the ones which rst contact the other contactmember wear down after a few operations of said switch so that all ofsaid ridges nally completely engage with said other member.

13. A switch comprising a hinge contact member, a blade member pivotedthereon, one of said members being provided with a contact portionhaving a plurality of projecting ridges concentric with the pivot axisfor engaging the other of said members, the outer ridges serving toprevent the entrance of dirt and other material into the contact area.

14. A switch comprising a hinge contact member, a blade member pivotedthereon, one of said members being .provided with a contact portionhaving a plurality of projecting ridges concentric with the pivot axisfor engaging the other of said members to prevent the entrance of dirtinto the contact area and to seal in a lubricant in the contact area.

15. A switch comprising a hinge contact member, a pair of switch bladespivoted thereon, said blades being provided with raised annular contactportions having a plurality of projecting ridges concentric with thepivot axis for engaging the hinge member, said ridges being of a sizesuch that any ridges which rst contact with the hinge member wear downafter a few operations of the switch until al1 of said ridges finallyengage the hinge member, the outer ridges serving to seal dirt out ofsaid contact area and to seal a lubricant in said contact area.

16. A switch comprising a hinge contact member, a blade member pivotedthereon, one of said members being provided with an annular raisedcontact portion concentric with the pivot axis and having a plurality ofconcentric sharp-edged ridges for engaging the other of said members,said raised contact portion and said ridges being formed by embossingthe same from the material of one of said members.

17. In an electrical switch, a contact tongue, a switch blade movableinto and out of engagement with said tongue, said blade being providedwith a raised contact portion of a length less than the width of saidtongue for engaging the central portion of the side surface of saidtongue, said contact portion having a knurled Contact surface providinga multiplicity of relatively sharp projections for engaging said tongue,

18. In an electrical switch, a pair of flat contact members, meansmounting said members in substantially parallel planes for relativemovement into mutual engagement, one of said members being provided witha raised restricted area contact portion having a plurality ofrelatively sharp-edged parallel ridges on its contact surface forengaging the other of said members, said ridges being disposed parallelto the direction of relative motion of the Contact portions of saidcontact members.

19. In an electrical switch, a pair of ilat contact members, meansmounting said members in substantially parallel planes for relativemovement into mutual engagement, one of said members being provided witha raised restricted area contact portion having a multiplicity ofrelatively sharp projecting points on its contact surface for engagingthe other of said members.

20. In an electrical switch, a pair of ilat contact members, meansmounting said members for relative movement into mutual engagement, oneof said members being provided with a contact portion having amultiplicity of parallel relatively sharp-edged ridges for engaging thesurface of the other of said members, said ridges being disposedparallel to the direction of relative motion of the contact portions ofsaid contact members as they move into engagement.

21. An electrical switch comprising a contact member, a cooperatingblade member, one of said members hav-ing opposed portions forcooperating with opposite side portions of the other member, saidcooperating portions of one of said members having raised restrictedarea contacts to provide high pressure restricted area contacts when theswitch is closed, said raised restricted area contact portions having amultiplicity oi closely spaced sharp edged projections for engaging thesurface of the other member, and operating means for opening and closingthe switch having force multiplying means operable to pry the highpressure limited area contacts out of high pressure engagement prior tomoving the blade member to open position.

22. In a circuit interrupter, a pair of cooperating contact members, oneof said members having a contact surface formed to provide amultiplicity of closely spaced sharp edged projections for engaging thecontact surface of the other contact member with the sharp edgespointing substantially normal to the contact surface of said othercontact member.

23. A circuit interrupter comprising a stationary contact member, acooperating movable contact member, said contact members having the formof flat bars mounted in substantially parallel planes, one of saidmembers having a contact portion provided with a multiplicity of closelyspaced relatively sharp edged parallel ridges for 4 engaging the surfaceof the other contact member with 'the sharp edges pointing substantiallynormal to the surface of said other contact member.

HERBERT J. CRABBS.

